(a) Technical Field of the Invention
The present invention generally relates to backlight modules for liquid crystal display devices, and more particularly to a frame structure for the assembly of the various components of a backlight module.
(b) Description of the Prior Art
A liquid crystal display (LCD) device requires a planar light source device to provide lighting having high uniformity, brightness, and a wide viewing angle. The planar light source device usually contains at least a backlight module and a front light module.
A conventional edge-lit backlight module, as shown in FIG. 1, mainly contains a frame structure 11, a reflection plate 12, a light guide plate. 13, optical films 14, and a light source unit 15 using, for example, cold cathode fluorescent lamp (CCFL).
The frame structure 11, usually made of a plastic material, contains a plate member 111 and a frame member 112. Along the edges 1111 of the plate member 111, there are a number of notches 1112, each of which has a hook element 1113 there within. The edges 1111 of the plate member 111 jointly confine a hollow area 1114 for accommodating the reflection plate 12 and the light guide plate 13 sequentially in this order from bottom to top inside the hollow area 1114. Along the edges (not numbered) of the frame member 112, there are clasp elements 1121 located correspondingly to the hook element 1113 of the plate member 111. When the frame member 112 is pressed against the plate member 111, their corresponding clasp elements 1121 and hook elements 1113 would interact to fixedly join the frame member 112 and the plate member 111 together. The optical films 14, including one or more diffusion sheets and prism sheets, are arranged on the surface of the light guide plate 13 for scattering the light to achieve better uniformity and for focusing the light into a proper viewing angle to achieve brightness enhancement. The elongated light source unit 15 is wrapped inside a reflector 16 to direct its light into a side of the light guide plate 13. The two ends of the light source unit 15 are configured with locking elements 151 to fix the light source unit 15 to the frame structure 11. The employment of the reflector 16 is to enhance the utilization of the light from the light source unit 15.
To assembly the backlight module 1 illustrated in FIG. 1, at first, the light source unit 15 is placed inside the reflector 16, and the light source unit 15 and the reflector 16 are fixed to a side of the frame structure 11. Then, the reflection plate 12 and the light guide plate 13 are placed in the hollow area 1114 of the plate member 111, with the light incidence side of the light guide plate 13 embedded into the opening of the reflector 16. The optical films 14 are then stacked on the light guide plate 13. At last, the frame member 112 is pressed against the plate member 111 so that their corresponding clasp elements 1121 and hook elements 1113 are locked to each other. The assembly of the backlight module 1 is then accomplished, whose result is shown in FIG. 2.
The locking mechanism of the conventional edge-lit backlight module 1 has some shortcomings. For example, since the frame structure 11 is made of a plastic material and has certain flexibility, when it is under a heavy pressure, the clasp elements 1121 would deform as it slides along the slope surface of the hook elements 1113 and escape from the confinement of the hook element 1113, as can be seen from FIG. 3. Without a strong support from the locking mechanism, the heavy pressure will land on the light source unit 15 as well, causing it to break in some worst-case scenarios.
To overcome the problem, there are vendors providing a different structure for the backlight module 2 as shown in FIG. 4, which also contains a frame structure 21, a reflection plate 22, a light guide plate 23, optical films 24, and a light source unit 25 using, for example, cold cathode fluorescent lamp (CCFL).
The frame structure 21, usually made of a plastic material, contains a plate member 211 and a frame member 212. Along the edges 2111 of the plate member 211, there are a number of notches 2112, each of which has a hook element 2113 there within. The edges 2111 of the plate member 211 jointly confine a hollow area 2114 for accommodating the reflection plate 22 and the light guide plate 23 sequentially in this order from bottom to top inside the hollow area 2114. Also along the edges 2111 of the plate member 211, there are a number of supporting rods 2115 extending upward for an appropriate distance above the edges 2111 of the plate member 211. Along the edges (not numbered) of the frame member 212, there are clasp elements 2121 located correspondingly to the hook element 2113 of the plate member 211. When the frame member 212 is pressed against the plate member 211, their corresponding clasp elements 2121 and hook elements 2113 would interact to fixedly join the frame member 212 and the plate member 211 together. The optical films 24, including one or more diffusion sheets and prism sheets, are arranged on the surface of the light guide plate 23 for scattering the light to achieve better uniformity and for focusing the light into a proper viewing angle to achieve brightness enhancement. The elongated light source unit 25 is wrapped inside a reflector 26 to direct its light into a side of the light guide plate 23. The two ends of the light source unit 25 are configured with locking elements 251 to fix the light source unit 25 to the frame structure 21. The employment of the reflector 26 is to enhance the utilization of the light from the light source unit 25.
To assembly the backlight module 2 illustrated in FIG. 4, at first, the light source unit 25 is placed inside the reflector 26, and the light source unit 25 and the reflector 26 are fixed to a side of the frame structure 21. Then, the reflection plate 22 and the light guide plate 23 are placed in the hollow area 2114 of the plate member 211, with the light incidence side of the light guide plate 23 embedded into the opening of the reflector 26. The optical films 24 are then stacked on the light guide plate 23. At last, the frame member 212 is pressed against the plate member 211 so that their corresponding clasp elements 2121 and hook elements 2113 are locked to each other. As such, the edges of the frame member 212 are also confined by the supporting rods 2115 of the plate member 211. The assembly of the backlight module 2 is then accomplished, whose result is shown in FIG. 5.
As shown in FIG. 6, because of the configuration of the supporting rods 2115, when the frame member 212 is under a heavy pressure, the supporting rods 2114 would prevent the clasp elements 2121 from sliding along the slope surface of the hook elements 2113 and thereby the clasp elements 2121 wouldn't deform and escape from the hook elements 2113, as can be seen from FIG. 6. However, the supporting rods 2115 would inevitably increase the planar area of the backlight module 2, which would cause some installation issues as the backlight module 2 is to be assembled into a final product along with other components of a LCD device.